Manufacture of ceramic ware



United States Patent 2 991 211 MANUFACTURE 01 CERAMIC WARE James A. Bower, Chester, W. Va., assignor to The Taylor,

Smith & Taylor (10., East Liverpool, Ohio, a corporation of West Virginia N0 Drawing. Filed Dec. 2, 1957, Ser. No. 699,948 13 Claims. (Cl. 154-95) The present invention relates to the manufacture of ceramic ware and, more particularly, to such ware known as pottery ware, porcelain ware and chin-a ware. More specifically, it relates to a method of manufacturing and decorating such ware.

In the manufacture of ceramic ware, and, more particularly, in the manufacture of the type of ware commonly referred to as pottery ware, it has been customary, during the manufacturing process, to decorate the ware. This is generally accomplished by the application of the desired design to the ware by means of a decalcomania transfer (decal) applied to the ware during the manufacturing operation. In some instances, the design is applied to the ware prior to the application of the glaze and, in other instances, the design is applied after glazing. The former is referred to as underglazing and the latter as overglazing decoration. It has been customary in both underglazing and overglazing operations to employ decals which, after the imprint thereon has been transferred to the ware, can be removed by water. More recently, however, it has been proposed to employ decals which can be released by heat and blown from the ware after the transfer of the design to the ware. Such decals have been used successfully in the overglazing decorating process, but heretofore it has not been possible to employ them satisfactorily for underglazing decorating operations.

By the present invention, I provide a method whereby such heat releasable decals can be employed successfully in a satisfactory commercial underglazing decorating operation.

The heat releasable decals are manufactured by first coating the face of the paper of the decal with a wax. Thereafter, the appropriate design in any desired color is impn'nted on the wax coated paper by any of the known processes, such as the silk screen process. The design is then coated with a varnish which may extend throughout the entire area of the decal, although, generally, the varnish coat is put on over the design and adjacent areas. In the use of such decals, the ware is heated to a temperature of about 250 F. The decal is placed in position 'face down on the heated ware and subjected to pressure. The wax melts and the design on the face is imprinted on the ware. Due to the melting or softening of the wax, the decal will be released and can be blown off the ware. However, due to the presence of the wax on the ware, at the point where the design is and adjacent thereto, it is not possible to thereafter satisfactorily apply the usual glaze without taking appropriate steps to remove the wax. Sufiicient of the wax cannot be removed by an ordinary rubbing operation to permit the application of a suitable glaze coat in the usual manner. The wax coating, of course, can be burned off, but this results in an additional and expensive manufacturing step. Considerable research and experimental work has been performed by those skilled in the art in order to render heat releasable decals usable in underglazing operations; but, prior to the making of my invention, such efforts were fruitless so far as developing a commercially practicable operation is concerned.

If the wax put on the ware in the decorating operation is not removed by burning, the glaze cannot be satisfactorily applied. The wax remaining on the ware evidently has a different surface tension than the glaze and,

2,991,211 Patented July 4., 1961 as a consequence, when the glaze is sprayed on or otherwise applied, it has a tendency to run off the wax or ball up on the wax with the result that an objectionable uneven glaze is formed on the ware. Some glaze may be retained on the decoration, but the non-uniformity of the glaze is highly objectionable and ware which is not uniformly glazed or which has bubbles or ungl-azed areas must be scrapped.

By my invention, I provide a process which overcomes the difficulties mentioned above and which permits the use of heat releasable decals in underglazing decorating operations without the necessity of removing the wax by burning or otherwise prior to the application of the glaze coating. I accomplish this objective by applying to the Ware, while at an elevated temperature, a relatively thin coating or layer of a glaze or other material compatible with the glaze to be applied later and allowing this thin protective layer or coating to dry prior to the application of the glaze. In the application of the heat releasable decals to the ware, the ware is heated to a temperature sufficient to soften or melt the wax. This temperature is approximately 200 to 250 F. The decal is then placed in position and pressed so as to effect the transfer of the design. The decal is then blown off. While the ware is still hot, the relatively thin coating or layer is applied. It may be a glaze or any of the materials commonly employed in glazing compositions or any other material compatible with the glaze in the sense that it will fuse with and not materially affect the characteristics of the glaze after firing, particularly its' transparency or translucency. This coating or layer may be put on the ware by spraying or in the form of a dry powder which will adhere to the ware at those areas which are covered with the wax. Thereafter, if sprayed on, it is allowed to dry, but, due to the fact that the wane is at an elevated temperature when the coating is applied, this requires only a matter of seconds. The ware can then be glazed, fired and otherwise finished or it may be allowed to cool and be stacked for future treatment.

It will be apparent from what has been stated that an important feature of the present invention resides in the application to the ware, when the ware is at an elevated temperature and after the backing of the decal has been removed, of a thin layer or coating of a material which will adhere to the ware, including the areas covered with the wax left by the decal and which will be compatible with the glaze to be applied subsequently in the sense that it will fuse with the glaze and not materially affect the characteristics of the fired glaze. The coating material also should have a lower surface tension than the wax in order to give proper coverage over the waxed areas and the texture of the surface of the waxed areas should be modified by the application of the coating so as to permit the subsequently applied glaze to cover all areas relatively uniformly.

In order to facilitate a clear understanding of the invention, it will be described somewhat more in detail as applied to the manufacture of pottery.

In the manufacture of such ware, the clays are mixed either in the dry state or in the wet state. After the clay has been prepared in one of the conventional manners, the biscuit is made on a jiggering machine or by casting. The biscuit is then fired in the conventional Way at a temperature in the neighborhood of 2,000 F. It is then ordinarily cooled to room temperature. Thereafter, the ware is placed in an oven, which may be of the continuous type, and heated to a temperature of approximately 250 F. It is then taken out of the oven and fed to a decal applying station where the decal is applied, either by hand or by machine. After the decal is applied, it is pressed against the ware in a suitable manner,

such as by a hydraulically operated press. This operation is performed while the ware is at the elevated temperature. After the decal has been subjected to appropriate pressure, an air blast is applied to the ware and the backing paper of the decal is blown loose. While the ware is still at a temperature of approximately 250 F., the thin coating or layer of material of the character described above is applied to the ware. The coating, if applied in the wet state, is allowed to dry. This drying operation is of exceedingly short duration (on the order of a few seconds) due to the fact that the ware is at an elevated temperature of about 200 to 250 F. at the time the coating is applied. Thereafter, the desired glaze may be applied or the ware may be allowed to cool and the glaze applied at a later time. After the glaze is applied, the ware is fired in the conventional manner at a temperature of approximately 1900 F.

While, as stated above, the coating which I provide can be applied while the ware is still hot immediately after the decal backing has been removed, the ware can be allowed to cool and, at a subsequent stage of the operation, it can be reheated to a temperature of between 200 F. and 250 F. and the coating applied at that time. However, for economical reasons, it is preferable to apply the coating immediately after the decal backing has been removed and while the ware is still hot. This avoids the necessity of a reheating operation and, in addition, provides protection for the design on the ware so that, if the ware is stacked at this stage, the color applied to one piece will not be transferred to another adjacent piece and will not be smeared or otherwise marred. This is because the coating, when applied before stacking, provides protection for the design applied to the ware.

The thin coating, as indicated above, can be applied either wet or in a dry state. It can be applied by a spraying operation or it can be dusted on or the ware can be passed through a dust room containing a dust of the requisite coating material.

After the coating has been applied, the were can be allowed to cool and can be stacked and stored before further manufacturing steps are carried out on it. Alternatively, it can be subjected to the usual glazing and final firing operations immediately after the application and drying of the thin protective coating.

Various materials can be used for the protective coating. The coating can be of the same material as the regular glaze to be subsequently applied. A typical example of such a glaze consists of a frit (made from borax, flint, whiting and boric acid), clay, flint, lead monosilicate, hydrate of alumina, spar, zinc oxide and whiting. The frit used in the glaze just mentioned may be used as the protective coating. An example of such a frit made from the materials mentioned above, namely, borax, flint, whiting and boric acid, will consist of sodium silicate, potassium silicate, calcium silicate and lead borosilicate. Other materials which may be used in place of the glaze or the frit described above are: white lead, red lead, litharge, lead monosilicate, lead bisilicate or feldspar. Bentonite may be used as a carrier with any of the above-mentioned materials. In addition, any of the materials mentioned as being embodied in the glaze specified above can be used for the protective coating.

While I have mentioned various materials which can be used, it will be understood that my invention is not limited to them as various other materials complying with the characteristics specified above may be used.

As indicated above, the protective layer may be applied in the wet state or in the dry state so long as some adhesion to the surface to which it is applied takes place. The material for the coating, when applied wet, may be in the form of an emulsion, a suspension or a solution.

While I have described my invention in detail as applied to the manufacture of pottery ware, it will be apparent that it may be applied in the manufacture of various other ceramic objects and that it may be practiced otherwise than specifically described above within the scope of the appended claims.

I claim:

1. In a process of manufacturing ceramic ware in which the ware is formed and in which a waxed paper backed decal is applied face-down under pressure at a time no later than at least prior to the application and firing of the glaze coating at an elevated firing temperature, the steps comprising heating the ware to a waxmelting temperature sufiicient to effect transfer of the applied decal from the face side of the paper back to the confronting ware surface to decorate it, removing the paper back by blowing it off such ware, and at a time while it is at an elevated temperature, applying to the decorated surface a thin coating of a material which will adhere to the surface of the ware and which is compatible with the glaze to be applied thereafter to the extent that it will fuse with the glaze and not materially affect the characteristics of the fired glaze.

2. In a process of manufacturing ceramic were in which the ware is formed and in which a waxed paper backed decal is applied face-down under pressure at a time no later than at least prior to the application thereto and the firing thereon of a glaze coating at an elevated firing temperature, the steps comprising heating the ware to a wax-melting temperature sufiicient to effect transfer of the applied decal from the face side of the paper back to the confronting ware surface to decorate it, removing the paper back by blowing it off such ware, and at a time while it is at an elevated temperature, applying to the decorated surface a relatively thin coating of a glazing material which, when dry, will adhere to the decorated surface of the ware and which is compatible with the glaze to be applied thereafter.

3. In a process of manufacturing ceramic ware in which the ware is formed and in which a waxed paper backed decal is applied face-down under pressure at a time no later than at least prior to the application thereto and the firing thereon of a glaze coating at an elevated firing temperature, the steps comprising heating the ware to a wax-melting temperature sufiicient to etfect transfer of the applied decal from the face side of the paper back to the confronting ware surface to decorate it, removing the paper back by blowing it off such ware, and at a time while it is at an elevated temperature, applying to the decorated surface a relatively thin coating of a glazing material which, when dry, will adhere to the decorated surface of the ware and which is compatible with the glaze to be applied thereafter, allowing the coating to dry, and thereafter applying a glaze and fusing the glaze.

4. In the manufacture of ceramic ware suited to rereceive an underglazing decoration by means of a waxed paper backed decal adapted to be applied face-down under pressure, the steps comprising forming the ware, heating the formed ware to a point at least at or above the wax-melting temperature, applying the waxed paper backed decal in the described manner to a surface of the ware, While the latter is hot, to release and to effect transfer of the decal decoration from the face side of the paper back to the confronting ware surface to decorate it, removing the paper back of the decal from such ware, applying to the decorated surface, substantially immediately while the were is still hot, at relatively thin coating of a material in a wet state which will adhere to and practically instantaneously dry upon the decorated surface of the ware and which is compatible with the glaze to be applied to the ware, thereafter glazing the ware and firing the glazed ware.

5. In the manufacture of ceramic ware suited to receive an underglazing decoration by means of a waxed paper backed decal adapted to be applied face-down un- Wax-melting temperature, applying the waxed paper backed decal in the described manner to a surface of the ware, while the latter is hot, to release and to effect transfer of the decal decoration from the face side of the paper back to the confronting ware surface to decorate it, removing the paper back of the decal from such ware, apply to the decorated surface, substantially immediately while the ware is still hot, a relatively thin coating of a material in a wet state which will adhere to and practically instantaneously dry upon the decorated surface of the ware and which is compatible with the glaze to be applied thereafter to the extent that it will fuse with the glaze and not materially aifect the characteristics of the glaze when fired, and thereafter applying a glaze coating and firing the glazed ware.

6. In the manufacture of ceramic ware, the steps comprising heating the formed ware, apply a decoration to at least one surface of the ware by means of a heat releasable decal having a waxed base, removing the decal backing, applying to the decorated surface of the ware, while the ware is at a temperature sufficient to melt any wax on the surface thereof, a thin coating of a material which will adhere to the decorated surface of the Ware and which is compatible with the glaze to be applied thereafter to the extent that it will fuse with the glaze and will not materially affect the transparency or translucency of the glaze, applying a glaze to the ware and firing the glazed ware.

7. In the manufacture of ceramic Ware, the steps comprising heating the formed ware, adhesively applying a decoration directly to at least one surface of the ware by .means of a heat releasable decal having a waxed base,

removing the decal backing, applying to the decorated surface of the ware, while at a temperature suflicient to melt any Wax on the surface thereof, a sprayed coating of a material which, when dry, will adhere to the decorated surface of the ware and which is compatible with the glaze to be applied thereafter, allowing the coating to dry, and thereafter glazing and firing the ware.

8. In the manufacture of ceramic ware, the steps comprising heating the formed ware, applying a decoration to at least one surface of the ware by means of a heat releasable decal having a waxed base, removing the decal backing, applying to the decorated surface of the ware, while at a temperature sufficient to melt any wax on the surfacethereof, a coating of a powdered material which will adhere to the decorated surface of the ware and which is compatible with the glaze to be applied thereafter, applying a glaze coating to the ware and thereafter firing the glazed ware.

9. In a process of manufacturing ceramic ware in which the ware is formed and then a surface thereof is decorated prior to the application thereto of a glaze coating and the firing of the coating thereon, the steps comprising heating the ware, decorating a surface of the ware, while it is at an elevated temperature, by means of a heat releasable decal, thereafter, while the ware is at an elevated temperature, applying to the ware surface a thin coating of a material which will adhere to the decorated surface of the ware and which is compatible with the glaze to be applied thereafter, and applying a glaze coating to the ware and firing the glazed ware.

10. In a process of manufacturing ceramic ware in which the ware is formed and then a surface thereof is decorated prior to the application thereto of a glaze coating and the firing of the coating thereon, the steps comprising heating the ware, decorating a surface of the ware, while the ware is at an elevated temperature, by means of a heat releasable decal, thereafter, while the ware is at an elevated temperature, applying to the decorated surface a thin sprayed coating of a glaze-like ma terial which will adhere to the decorated surface of the ware, drying the coating, and thereafter glazing and firing the ware.

11. In a process of manufacturing ceramic ware in which the ware is formed and then a surface thereof is decorated prior to the application thereto of a glaze coating and the firing of the coating thereon, the steps comprising heating the ware, decorating a surface of the ware, while the ware is at an elevated temperature, by means of a heat releasable decal, thereafter, while the ware is at an elevated temperature, applying to the decorated surface by dusting thereon a relatively thin coating of a glaze-like material which will adhere to the surface of the Ware, and thereafter glazing and tiring the ware.

12. In a process of manufacturing ceramic ware in which the ware is formed and then a surface thereof is decorated prior to the application thereto of a glaze coating and the firing of the coating thereon, the steps comprising heating the ware, decorating a surface of the ware, while the ware is at an elevated temperature, by means of a heat releasable decal, thereafter, while the ware is at an elevated temperature, applying to the decorated surface of the ware a relatively thin coating of a constituent of a glazing material which will adhere to the decorated surface of the ware, and thereafter glazing and firing the ware.

13. In a process of manufacturing ceramic ware in which the ware is formed and then a surface thereof is decorated prior to the application thereto of a glaze coating and the firing of the coating thereon, the steps comprising heating the ware, decorating a surface of the ware, while the ware at an elevated temperature, by means of a heat releasable decal, thereafter, while the ware is at an elevated temperature, applying to the decorated surface of the ware a thin coating of a material having a lower surface tension than the wax from the decal and which is compatible with the glazing material to be employed, and thereafter glazing and firing the ware.

References Cited in the file of this patent UNITED STATES PATENTS 186,112 Cliff et al Jan. 9, 1877 1,656,260 Zeh Ian. 17, 1928 2,044,922 Swift et a1 June 23, 1936 2,419,918 Sheetz Apr. 29*, 1947 2,476,570 Van Horn et a1. July 19, 1949 2,708,172. Robson May 10, 1955 2,734,840 Kane Feb. 14, 1956 

1. IN A PROCESS OF MANUFACTURING CERAMIC WARE IN WHICH THE WARE IS FORMED AND IN WHICH A WAXED PAPER BACKED DECAL IS APPLIED FACE-DOWN UNDER PRESSURE AT A TIME NO LATER THAN AT LEAST PRIOR TO THE APPLICATION AND FIRING OF THE GLAZE COATING AT AN ELEVATED FIRING TEMPERATURE, THE STEPS COMPRISING HEATING THE WARE TO A WAXMELTING TEMPERATURE SUFFICIENT TO EFFECT TRANSFER OF THE APPLIED DECAL FROM THE FACE SIDE OF THE PAPER BACK TO THE CONFRONTING WARE SURFACE TO DECORATE IT, REMOVING THE PAPER BACK BY BLOWING IT OFF SUCH WARE, AND AT A TIME WHILE IT IS AT AN ELEVATED TEMPERATURE, APPLYING TO THE DECORATED SURFACE A THIN COATING OF A MATERIAL WHICH WILL ADHERE TO THE SURFACE OF THE WARE AND WHICH IS COMPATIBLE WITH THE GLAZE TO BE APPLIED THEREAFTER TO THE EXTENT THAT IT WILL FUSE WITH THE GLAZE AND NOT MATERIALLY AFFECT THE CHARACTERISTICS OF THE FIRED GLAZE. 